The present invention relates to a vibration damper/isolator for a control valve, such as a steam control valve.
Control valves for controlling the flow of fluids are well known in the art. In a nuclear power generating system, control valves are employed for controlling the flow of fluids, such as steam. Past nuclear control valves have experienced significant problems due to the severe conditions in which they are operated.
Steam control valves in nuclear power generating facilities are generally relatively large in comparison to steam control valves used in other power generating facilities, e.g., fossil fuel facilities. The use of larger valves in nuclear power facilities is due, in part, to the generally lower energy steam produced by nuclear facilities as compared to fossil fuel facilities. These larger valve structures tend to exhibit problems which may not be as significant in smaller valve structures. For example, typical steam control valves used in power facilities must be operable to close a steam path within a short period of time. Thus, the valve plug employed in such valves must be able to move to a position which blocks or closes the steam path at a high speed. In order to ensure quick movements of the relatively large valve plug assembly employed in most nuclear control valves, the valve plug should not be so tightly fit within a valve bonnet that movement of the valve plug along the axis of the bonnet would be significantly restricted or slowed. However, past valve designs include a valve plug which is so loosely fit within the valve bonnet that the valve plug tended to vibrate laterally with respect to the valve bonnet.
Thus, a common problem which such past nuclear steam control valves have experienced is significant vibrations of the operating parts of the valves. These vibrations are generally high frequency vibrations induced by a fluid flow, e.g., steam flow, across the valve seat. The frequencies of vibrations induced by steam flow generally occur across a broad spectrum of the audio frequency range. For example, such frequencies as K.degree.85 Hz, where K=0, 1, 2 . . . , have been noted. A large portion of the noted vibration energy tends to occur in the 300-400 Hz range.
Such vibrations can cause severe wear and damage to the internal valve components. For example, cracks in valve components, including housings and mufflers, and excessive wear to valve liners, seal ring slots, valve stems and valve stem bushings have been attributed to such vibrations. Additionally, such vibrations have been known to cause damage to external operating systems mounted on or with valve bonnets. Moreover, such vibrations have been known to cause excessive noise transmissions into the turbine room floor area of nuclear facilities.